For a construction machine such as a hydraulic exactor, it is preferable that energy saving is carried out upon various operations such as swiveling, traveling, excavating, landing, or loading, since working speed and amount are significantly varied depending upon a kind of operation. For example, the excavator usually selects either high speed or low speed upon traveling, and selects either heavy excavating operation or light excavating operation upon excavating.
An excavator of a related art includes an engine revolution speed control switch 100 and a mode selection switch 200, as illustrated in FIG. 1, so that a driver can control an engine revolution speed by rotating the engine revolution speed control switch 100 to an appropriate level or switching the mode selection switch 200 to a heavy excavating mode, a standard excavating mode or a light excavating mode, in accordance with working circumferences.
However, since the engine revolution speed control switch 100 and the mode selection switch 200 are configured as a dial manner which is manually operated, it is difficult to manipulate the switches precisely. Consequently, if it is set to a level higher than a standard engine revolution speed suitable for the working circumferences, it is likely to have serious problems such as excessive consumption of fuel, overload of the engine, or overheating of the engine. On the contrary, if it is set to a low level, there is a problem in a shortage of power.
Further, in order to manipulate the engine revolution speed control switch 100 and the mode selection switch 200, after a driver takes his hands off a manipulation lever and interrupts the working, the driver has to manipulate the switches. Therefore, there is a problem of deteriorating a working efficiency because of a vacuum in working.